Method and apparatus of refrigeration



Feb. 13, 1934. IR. K. HOMER A A ,946,854

METHOD AND APPARATUS OF REFRIGERATION Fi'ld Jan. 4, 1933 v Patented Feb. 13, 1934 UNITED STATES METHOD AND APPARATUS OF REFRIGERATION Robert K. Homer, Flint, Mich.

Application January 4, 1933. Serial No. 650,158 4 Claims. (01. 62-116) This invention relates to refrigeration, and particularly to the refrigeration of substances which would be injured by desiccation, for example, food stufis.

The object of the invention is to combine the advantages of mechanical refrigeration with the advantages of refrigeration by the use of melting ice exposed directly to the air in the refrigerated chamber. The invention is particularly applicable to domestic refrigeration, and will be described as, so applied, but it is generally applicable to refrigeration where similar conditions are encountered, and limitation to the domestic field is not implied.

In conventional mechanical refrigerators, as at present constructed, whether the evaporator be directly exposed to the air in the refrigerated chamber, or whether it be submerged in a nonfreezing bath which serves as a heat reservoir, the surface exposed within the refrigerated chamber is at sub-freezing temperature. The purpose is to permit the use of an evaporator of small size, and to permit the freezing of a small supply of ice for domestic use. From this practice serious difficulties flow.

The heat gradient from the food stuffs, which are in the neighborhood of 50 52, through the air in the refrigerator, which is at an intermediate temperature, to the evaporator, which is at the lowest temperature in the refrigerator, is substantial. The air rapidly loses its moisture to the evaporator, where it collects as frost. The air thus. becomes a highly effective drying medium and abstracts moisture from warmer moist substances in the refrigerator. This drying action can be prevented by using hermetically closed containers for the food products, but this is obviously impracticable.

Since the evaporatorcoil, in the commercial types of refrigerator, is the sole source of refrigeration, the refrigerating unit must be larger than necessary to carry the average refrigerating load. Otherwise it would be insufllcient to carry the peak load. Such an oversized mechanical unit must be equipped with relatively complicated automatic means to put it into and out of action, and thus maintain a substantially uniform temperature in the refrigerator. Intermittent operation entalls starting losses of moment. Conventional mechanical refrigerators consequently are expensive to construct, and do not operate as economically as would a continuously active unit.

In a refrigerator using melting ice, the temperature gradient from the food stuffs to the ice is less. The melting of the ice results in the presence of water within the refrigerated space.

This water, flowing in contact with drip trays and other parts of the refrigerator structure, ac-

) quires a temperature substantially above the freezing point of water and competes with the food stuffs, if it does not entirely supplant them. as a source of moisture to humidify the air. The air tends to give up moisture to the ice just as in the mechanical refrigerator it tends to give up moisture to the evaporator, but in the iced refrigerator the temperature gradient is less and the rate of transfer of moisture to the ice is conse:- quently less.

As a practical. matter, there is little or no drying effect upon food stuffs kept in an iced refrigerator in which the ice melts normally in contact with the air in the refrigerator. This procedure has another marked advantage in that the water produced by meltage of the ice, absorbs odors from the air and carries them away through the drain.

In fact, the only objections to ice refrigeration,

for domestic purposes, are the need for frequent icing, the rise of temperature which occurs as the ice supply becomes depleted, and undue operating expense.

, The present invention combines the advantages of both systems by relating them in a special way. According to the invention, a refrigerator which is virtually an ordinary ice refrigerator, is equipped with mechanical refrigeration of any suitablev type, to abstract heat from the refrigerator at a rate which approximates the minimum in-leakage of heat into the refrigerator. This mechanical refrigerating unit operates substantially at or slightly above the freezing temperature of water, so that frost will not form upon the cooling unit.

Where a refrigerating unit of the compressor. condenser, expander type is used, it is only large enough to carry approximately the refrigerating load, and it operates continuously.

The refrigerator is iced, as usuaLbut since the mechanical unit carries the greater portion of the refrigerating load, the periods between icing are long, say a week or even more. The ice serves as a stabilizing medium for both temperature and humidity, and supplies any deficiency of refrigeration when the demands for refrigeration are heavy. The ice is available for incidental domes-.

tic uses, so that the absence of freezing capacity in the mechanical unit is not an objectionable factor.

The advantages of this arrangement are many. The mechanical unit is small and inexpensive because it meets approximately the minimum demand for refrigeration. 'It is free from starting losses because it operates continuously. It is of the utmost simplicity because it requires no automatic control whatsoever. The ice serves as a reserve of refrigeration, and also to maintain substantially saturated humidity conditions. By proper design the intervals between icing can bemade quite long. In fact, icing can be dispensed with without a complete loss of refrigeration.

The dehydration of food stuffs and the necessity for defrosting the evaporator, characteristic of the present mechanical refrigeration, are both avoided. The odor absorbing characteristics of melting ice are secured. The first cost and the operating cost are both minimized. The refrigerator of the present invention gives continuously the optimum effect of an iced refrigerator. The mechanical unit is not required to develop as low a temperature as where freezing of ice is necessary, and consequently it operates at a much greater efliciency because of the higher suction pressure of the refrigerant.

The invention will now be described in connection with the accompanying drawing, in which the single figure is a front elevation of a domestic refrigerator embodying my invention, with its door open.

In the drawing 1 represents the insulated shell of the refrigerator and 2 represents the usual door hinged thereto, and normally maintained closed by a latch of familiar form. The ice chamber is generally indicated by the numeral 3, and in normal operation contains a block of ice, indicated by the numeral vi. The ice chamber 3 is separated from the food space in the refrigerator by vertical partition 5, which terminates short of the top of the refrigerated space, leaving an air port 6, and by the drip collecting bottom 7, which is provided with an air port 8, the latter being protected by an umbrella or drip deflector.

9. The melted ice or drip is collected by the bottom 7 and delivered to a drip pipe 10 which conducts the drip outside the refrigerated chamber through the usual water seal or trap 11. A number of shelves 12, which are constructed in the form of gratings to permit the circulation of air,

' as usual, are provided. The circulation is upward through the shelves 12, then to the left I through port 6 and then downwardly through the ice chamber, returning by the port 8 to the food space in the refrigerator.

Mounted in the top of the ice chamber 3 is the heat absorbing element 13 of the mechanical refrigerating system. It is immaterial what this system is, and the heat absorbing element 13 might be a brine coil or it might be the evaporator of a mechanical system of the compressor, condenser expander type.

For purposes of illustration an evaporator of the last-named class is shown, 14 representing some regulating device conducting liquid refrigerant from the air-cooled condenser 15 to the evaporator 13. The condenser 15 is connected by the high pressure line' 16 with the discharge of a motor driven compressor 17. The suction of the compressor 17 is connected by the suction line 18 with the evaporator 13.

The representation of the mechanical refrigersting system in the drawing is purely conventional, and it is understood that this may be of any suitable type, provided it is capable of main taining the evaporator 13 constantly at a substantially uniform temperature. This temperature is as low as is practicable without the formation of frost on the evaporator 13.

The surface of the evaporator 13 is so coordinated with the average heat inleakage into the refrigerator, that if the mechanical refrigerating lystem is constantly operated, the absorption of heat by the coil 13 will approximate but not exceed the minimum inleakage of heat into the refrigerator. The cake of ice 4 is relied upon to furnish the additional requirements of refrigeration and carry any peak demands for refrigeration that may be encountered from time to time.

In use, a substantial quantity of ice is maintained in the chamber 3 at all times, and the compressor 1'7 is operated continuously so that the evaporator 13 is continuously effective. Under these conditions, the evaporator 13 carries substantially the entire refrigerating load at a temperature which will not produce frosting of the evaporator.

. The remainder of the refrigerating load, which will vary in amount, is carried by the block of ice. Consequently, the ice melts, but melts very slowly and the humidity conditions in'the refrigerator closely approximate the humidity conditions that 'chanical refrigerating system is subject to wide variation. Similarly, the construction of the refrigerator, particularly with respect to the arrangement of the ice chamber, is subject to the same variation that is encountered in ordinary refrigerators of the iced type.

The evaporator 13 is preferably placed in advance of and in close proximity to the ice with reference to the direction of the air circulation, but will function reasonably well located in some other position.

While I prefer that the evaporator 13 shall never be operated cold enough to induce frosting, slight frosting if intermittent, while the compressor 17 remains in operation, will not completely defeat the operation of the invention.

What is claimed is:

1. In a refrigerator, the combination of aheat 115 insulated casing; means for supporting ice within said casing and for directing either a thermosiphon or forced air circulation through said refrigerator and in contact with said ice; a mechanical heat absorbing unit also mounted in said refrigerator in the path of such circulation; and constantly operating means for withdrawing heat from said heat absorbing unit and serving to maintain the same at a substantially uniform temperature approximating but above the freezing temperature of water. I

2. The combination of claim .1, further characterized in that the heat absorbing capacity of said element at the stated temperature approximates the heat inleakage into said refrigerator.

3. The method of maintaining a desired cold temperature and saturated humidity conditions in an enclosed space substantially insulated against the entrance of heat, which consists in producing in said space a convection circulation of air in which it is first chilled by contact with a dry refrigerated surface maintained at a temperature approximating the freezing temperature of water and then by direct contact with a body of melting ice. 4

4. The method of claim 3, further characterized in that the refrigerating capacity of the dry refrigerated surface is such as to carry a substantial part of the entire refrigerating load, whereby the consumption of ice is minimized.

ROBERT K. HORNER. 

